I'm thinking the 6 core FX-6300 would be a good CPU which shouldn't overwhelm the Voltage Regulation on the board. It will not give the performance of a newer i5 but it should get you close. I'm not sure if a BIOS update would be needed to run that CPU.
For a PSU, I would suggest the XFX 550 Pro as an option or, if wanting something modular, the SeaSonic M12II 620W both are well received units made by SeaSonic (one of the top PSU manufacturers)